Ab initio calculations of group IVA tetrachloride complexes: VII. Structure and dynamics of the formation of GeCl<Subscript>4</Subscript> complexes with hexamethylphosphoric triamide

Quantum-chemical calculations by the RHF/6-31G(d) method were performed for the systems GeCl₄←[N(CH₃)₂]₃ and GeCl₄←₂OP[N(CH₃)₂]₃ with full geometry optimization and varied Ge←O distances. The calculations with full geometry optimization gave trigonal-pyramidal and trans-octahedral structures, respectively, which agrees with experimental NQR data. As the components of a system get closer together, mutual polarization followed by electron density transfer from H atoms of the electron donor onto Cl atoms of the electron acceptor take place. The O and Ge atoms act as conductors in this electron density transfer. Nonempirical quantum-chemical calculations do not reproduce adequately the p _σ density of the axial Cl atom in the trigonal-bipyramidal complex.     

Ab initio calculations of complexes of group IVA element tetrachlorides: II. Dynamics of complex formation of GeCl4 with trimethylamine

RHF/6-31G(d) calculations of the system GeCl₄←N(CH₃)₃ were performed with full geometry optimization and at varied Ge←N distance. Mutual approach of the system components is accompanied by their mutual polarization followed by electron density transfer from the H atoms of the donor to the Cl atoms of the acceptor. The C, N, and Ge atoms act merely as conductors of this electron density. The total energy of the system decreases until the Ge←N distance of 3.412 Å is attained; at this distance, however, the complex is not yet formed. The complex formation involves an increase in the energy by 0.213 eV. The applicability of the RHF/6-31G(d) method to studying the trigonal-bipyramidal complex was assessed.     

Ab initio calculations of group IVA tetrachloride complexes: V. Dynamics of the formation of the complex of SiCl<Subscript>4</Subscript> with tetramethylurea

Quantum-chemical calculations of the system SiCl₄←OC[N(CH₃)₂]₂ were fulfilled by the RHF/6-31G(d) method with full geometry optimization and at varied Si←O distances. The calculation with full geometry optimization does not lead to the unusual trigonalbipyramidal structure of the complex, found experimentally, and this structure is reproduced when the right angles between axial Si-Cl bonds and the coordination Si←O bond were set. Complex formation results in electron density transfer from the carbonyl C atom and from the H atoms of the electron donor, as well as from the Si atom is transferred mainly on axial Cl atoms [basically, on their p _z (p _σ) orbitals]. The total energy of such complex is higher by 0.936 eV than that of the most energetically favorable form of the studied system.     

Ab initio calculations of complexes of tetrachlorides of Group IVA elements: VIII. Structure of SiCl<Subscript>4</Subscript> complexes with hexamethylphosphoric triamide and dynamics of their formation

Quantum-chemical calculations of the systems SiCl₄←OP[N(CH₃)₂]₃ and SiCl₄←2OP[N(CH₃)₂]₃ with complete optimization of their geometry at various Si←O distances were performed by the RHF/6-31G(d) method. The first system was also calculated by the MP2/6-31G(d) method. The calculations of the systems with the complete geometry optimization resulted in trigonal-bipyramidal and trans-octahedral structures, respectively, having energy minima. When the components of the latter system approach each other, first their mutual polarization occurs, and then it is accompanied by electron density transfer from the H and P atoms of the electron-donor molecules to the Cl atoms of the acceptor. The results of the calculation of the trans-octahedral complex agree with the experimental ³⁵Cl NQR data. The electron density of Cl atoms increases upon complex formation, mainly due to an increase in their p _σ electron density.     

Nature of the coordination bond in the GeCl4-trimethylamine complex

Quantum-chemical computations were performed for the GeCl₄ ← N(CH₃)₃ system using the MP2/6-31G(d) method with total optimization of its geometry and at different fixed Ge…N distances (from 2.0 to 4.5 Å). The coordination bond in the complex results from the involvement of different AOs of Ge and N atoms (along with other atoms in the molecule) in the formation of a number of MOs. The number of these MOs increases with decreasing Ge…N distance, thus reducing the total energy of a molecule and stabilizing it. The coordination bond and the covalent bond are of the same nature. When the distance between the components of the system is reduced, the partial negative charges of N, C, and all Cl atoms increase; the partial positive charges of Ge and H increase as well.     

Structure of 2-methyl-3-(trichlorogermyl)propionic acid N,N-dimethylamide and the nature of the Ge←O coordination bond according to the ab initio calculation

Calculations of the molecule of 2-methyl-3-(trichlorogermyl)propionic acid N,N-dimethylamide with full and partial optimization of its geometry were performed by the RHF/6-31G(d) method. The total energy of this molecule which includes a pentacoordinated germanium atom (I) is by 3.84 kcal mol^?1 lower than if it contains a tetrakoordinated germanium (II). The mutual approach of Ge and O coordination centers as a result of their electrostatic interactions in the molecule (I) is shown to result in the formation of a Ge←O coordination bond, which provides an electron density transfer from the peripheral atoms of the donor fragment of the molecule to the atoms of the germanium coordination polyhedron. The Ge and O coordination centers of the molecule serve as conductors of the electron density. At the formation of Ge←O bond the electron density on the oxygen atom increases, while on germanium decreases.     

Ab initio calculations of complexes of group IVA element tetrachlorides: II. Dynamics of complex formation of GeCl4 with pyridine

RHF/6-31G(d) calculations of the trans-octahedral complex of GeCl₄ with pyridine were performed with full geometry optimization and at varied coordinate of the complexation reaction. The results obtained do not confirm the hypothesis that the complex is formed owing to interaction of the N atom with unoccupied d orbitals of the Ge atom. The complex formation is initiated by the interaction of the coordination centers (Ge and N), resulting in mutual approach of the system components, their polarization, and, when the distance between the components becomes sufficiently short, transfer of the electron density from the H and C atoms of the electron donor to the Cl atoms of the acceptor. In the process, a multicentered bond involving all the atoms of the Ge coordination polyhedron is formed.     

Synthese,Struktur und Eigenschaften von [nacnac]MX3‐Verbindungen (M = Ge,Sn; X = Cl,Br, I)

Synthesis, Structure, and Properties of [nacnac]MX₃ Compounds (M = Ge, Sn; X = Cl, Br, I) Reactions of [nacnac]Li [(2,6‐ⁱPr₂C₆H₃)NC(Me)C(H)C(Me)N(2,6‐ⁱPr₂C₆H₃)]Li ( 1 ) with SnX₄ (X = Cl, Br, I) and GeCl₄ in Et₂O resulted in metallacyclic compounds with different structural moieties. In the [nacnac]SnX₃ compounds (X = Cl 2 , Br 3 , I 4 ) the tin atom is five coordinated and part of a six‐membered ring. The Sn–N‐bond length of 3 is 2.163(4) Å and 2.176(5) Å of 4 . The five coordinated germanium of the [nacnac]GeCl₃ compound 5 shows in addition to the three chlorine atoms further bonds to a carbon and to a nitrogen atom. In contrast to the known compounds with the [nacnac] ligand the afore mentioned reaction creates a carbon–metal‐bond (1.971(3) Å) forming a four‐membered ring. The Ge–N bond length (2.419(2) Å) indicates the formation of a weakly coordinating bond.     

An ab initio study of the electronic and steric structure of Cl<Subscript>2</Subscript>ZX molecules (Z = P and As)

The electronic and steric structure of the Cl₂ZX molecules [Z = P and As, X = C₂H₅, N(CH₃)₂, and OCH₃] was examined by RHF/6-31G(d) and MP2/6-31G(d) calculations. The data on the electron distribution at the Cl atoms are compared with the published ³⁵Cl NQR data. The main reason for a decrease in the NQR frequency of the molecules with X = N(CH₃)₂ and OCH₃ as compared to the ethyl-substituted compounds is an increase in the population of the 3p components of their p _z(p _σ) orbitals. With X = N(CH₃)₂, electron distribution at two Cl atoms differs significantly.     

catena‐Poly­[[tetrakis(2‐allyl­tetrazole‐κN4)‐tetra‐μ‐chloro‐tricopper(II)]‐di‐μ‐chloro]

In the crystal structure of the title compound, [Cu₃Cl₆(C₄H₆N₄)₄]_n, there are three Cu atoms, six Cl atoms and four 2‐allyl­tetrazole ligands in the asymmetric unit. The polyhedron of one Cu atom adopts a flattened octahedral geometry, with two 2‐allyl­tetrazole ligands in the axial positions [Cu—N4 = 1.990 (2) and 1.991 (2) Å] and four Cl atoms in the equatorial positions [Cu—Cl = 2.4331 (9)–2.5426 (9) Å]. The polyhedra of the other two Cu atoms have a square‐pyramidal geometry, with three basal sites occupied by Cl atoms [Cu—Cl = 2.2487 (9)–2.3163 (8) and 2.2569 (9)–2.3034 (9) Å] and one basal site occupied by a 2‐allyl­tetrazole ligand [Cu—N4 = 2.028 (2) and 2.013 (2) Å]. A Cl atom lies in the apical position of either pyramid [Cu—Cl = 2.8360 (10) and 2.8046 (9) Å]. The possibility of including the tetrazole N3 atoms in the coordination sphere of the two Cu atoms is discussed. Neighbouring copper polyhedra share their edges with Cl atoms to form one‐dimensional polymeric chains running along the a axis.     

Ab initio calculations of group IVA tetrachloride complexes: IV. Dynamics of the formation of the complex of SiCl<Subscript>4</Subscript> with trimethylamine

Quantum-chemical calculations of the system SiCl₄←N(CH₃)₃ were fulfilled by the RHF/6-31G(d) and B3LYP/6-311G(d) methods with full geometry optimization at varied Si←N distances. The experimental electronic and steric structure of the complex were fit not on full geometry optimization but on the geometry optimization with the Si←N distance fixed at the experimental estimate. The calculations showed that the components polarize each other as come closer together. Furthermore, the electron density is transferred from the H atoms of the donor onto the Cl atoms of the acceptor. The C, N, and Si atoms serve only as electron density conductors. Original Russian Text V.P. Feshin, E.V. Feshina, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 5, pp. 786–791. For communication XX, see [1].     

An N‐Heterocyclic Silylene‐Stabilized Digermanium(0) Complex

The synthesis of an N‐heterocyclic silylene‐stabilized digermanium(0) complex is described. The reaction of the amidinate‐stabilized silicon(II) amide [LSiN(SiMe₃)₂] ( 1 ; L=PhC(NtBu)₂) with GeCl₂?dioxane in toluene afforded the Si^II–Ge^II adduct [L{(Me₃Si)₂N}Si→GeCl₂] ( 2 ). Reaction of the adduct with two equivalents of KC₈ in toluene at room temperature afforded the N‐heterocyclic carbene silylene‐stabilized digermanium(0) complex [L{(Me₃Si)₂N}Si→ Ge?Ge←Si{N(SiMe₃)₂}L] ( 3 ). X‐ray crystallography and theoretical studies show conclusively that the N‐heterocyclic silylenes stabilize the singlet digermanium(0) moiety by a weak synergic donor–acceptor interaction.     

A New Approach to the Design of Neutral 10‐C‐5 Trigonal‐Bipyramidal Carbon Compounds: A “π‐Electron Cap” Effect

DFT (B3LYP, M06‐2X) and MP2 methods are applied to the design of a wide series of the potentially 10‐C‐5 neutral compounds based on 6‐azabicyclotetradecanes: XC¹(YCH₂CH₂CH₂)₃N 1 – 3 , XC¹(YC₆H₄CH₂)₃N 4 – 6 , XC¹[Y(tBuC₆H₃)CH₂]₃N 7 – 9 and carbatranophanes 10 – 25 (X=Me, F, Cl; Y=O, NH, CH₂, SiH₂; Z=O, CH₂, (CH₂)₂, (CH₂)₃). Carbatranophanes 10 – 25 are characterized by a sterical compression of their axial 3c–4e XC¹←N fragment with respect to that in the parent molecules 4 – 6 . A magnitude of the revealed effect depends on a valence surrounding of the central carbon atom C¹, the size and the nature of the side chains (Z) that link the “π‐electron cap” with a tetradecane backbone. This circumstance allowed us to obtain 10‐C‐5 structures with the configuration of the bonds around the C¹ atom, which corresponds to practically an ideal trigonal bipyramid. In these compounds, the values of the covalence ratio χ of approximately 0.6 for the coordination C¹←N contacts with a covalent contribution (atoms in molecules (AIM) and natural bond orbital (NBO)) are record in magnitude. These values lie close to a low limit of the interval of the χ_Si←D change (0.6–0.9) being characteristic of the dative and ionic‐covalent (by nature) Si←D bond (D=N, O) in the known 10‐Si‐5 silicon compounds.     

Crystal structures of copper(II) complexes with methyliminodiacetate ions and 1,10-phenanthroline or imidazole [Cu(Phen)H<Subscript>2</Subscript>O][Cu(Mida)<Subscript>2</Subscript>]·2H<Subscript>2</Subscript>O and [Cu(Mida)Im]

Methyliminodiacetic acid (H₂Mida) and imidazole react with copper(II) to form crystals of the square pyramidal complex [Cu(Mida)Im]. One N and two O atoms of the Mida ligand (Cu-N 2.010(1) Å, Cu-O 1.955(1) Å, and 1.978(1) Å) and the imidazole N atom (1.950(1) Å) lie at the base of the pyramid. The carboxyl O atom of the neighboring complex lies at the apical position (2.411(1) Å); in this way the individual complexes are linked into infinite zigzag chains. Substitution of imidazole by 1,10-phenanthroline gave [Cu₂(Mida)₂(Phen)H₂O]·2H₂O crystals with two nonequivalent centrosymmetric octahedral anions [Cu(Mida)₂]^2? of face type (Cu-N 2.023 Å and 2.028(2) Å, Cu-O_ax 2.579 Å and 2.530(2) Å, Cu-O_bas 1.952 Å and 1.936(2) Å). The anions serve as bridges in chains between the [Cu(Phen)H₂O]²⁺ cation fragments to which they are bonded by their axial carboxyl groups. The Cu atom of the cation has a [4+1] environment (with the H₂O molecule lying on the axis of the pyramid, and with two N atoms of the ligand and two O atoms of the anions lying at the base).     

The layered structure of poly­[[di‐μ‐chloro‐bis­[chloro(2‐ethyl­tetrazole‐κN4)copper(II)]]‐di‐μ‐2‐ethyl­tetrazole‐κ2N1:N4]

In the polymeric title complex, [CuCl₂(C₃H₆N₄)₂]_n, there are two ligands in the asymmetric unit. The Cu atom adopts an elongated octahedral geometry, with two 2‐ethyl­tetrazole ligands [Cu—N = 2.0037 (16) and 2.0136 (16) Å] and two Cl atoms [Cu—Cl = 2.2595 (6) and 2.2796 (6) Å] in equatorial positions. A Cl atom and a symmetry‐related 2‐ethyl­tetrazole mol­ecule [Cu—Cl = 2.8845 (8) Å and Cu—N = 2.851 (2) Å] lie in the axial positions of the octahedron. One of the two 2‐­ethyltetrazole ligands of the asymmetric unit exhibits bidentate binding to two Cu atoms through two N atoms of the tetrazole ring, whereas the other ligand is coordinated in a monodentate fashion via one tetrazole N atom. The Cu‐atom octahedra form dimer entities by sharing edges with equatorial and axial Cl atoms. The dimers are linked together through the 2‐ethyl­tetrazole ligands to form one‐dimensional polymeric zigzag chains extending along the b axis. The chains are connected into infinite layers parallel to the (10) plane via the 2‐ethyl­tetrazole ligands.     

Hexa­aqua­bis­(di­methyl sulfoxide)­yttrium(III) trichloride

The title compound, [Y(C₂H₆OS)₂(H₂O)₆]Cl₃, contains the cation [Y(H₂O)₆{(CH₃)₂SO}₂]³⁺ with a distorted square antiprismatic geometry of the eight coordinated O atoms. The six water mol­ecules are coordinated with an average Y—O distance of 2.38 (2) Å, ranging from 2.360 (3) to 2.404 (3) Å. Each water mol­ecule forms two hydrogen bonds to the chloride anions with O—Cl distances ranging from 3.068 (4) to 3.422 (4) Å. The two di­methyl­ sulfoxide ligands, situated in the cis position with the O—Y—O angle equal to 83.22 (11)°, have Y—O distances of 2.269 (3) and 2.278 (3) Å.     

Hydrolysis of coordinated aminoacetonitrile in a platinum(IV) complex. Crystal structure of [PtPy(NH<Subscript>2</Subscript>CH<Subscript>2</Subscript>COO)Cl<Subscript>3</Subscript>]

Heating of a hydrochloric acid solution of trans-PtPy(NH₂CH₂CN)Cl₄ results in the hydrolysis of coordinated aminoacetonitrile to aminoacetic acid with the formation of a five-membered chelate ring attached to platinum through the nitrogen atom of the amino group and the oxygen atom of the carboxy group. X-ray diffraction analysis of [PtPy(NH₂CH₂COO)Cl₃] is carried out. The crystals are monoclinic: space group C2/c, a = 21.704(2), b = 8.7027(7), c = 15.576(1) Å, β = 126.606(1)^o, V = 2361.8(3) ų, Z = 8; R _hkl = 0.057, wR = 0.141. In the neutral complex, the Pt atom has a distorted octahedral coordination. The equatorial plane is formed by a Cl atom (Pt-Cl, 2.284(3) Å), the N atom of the Py molecule (Pt-N, 2.062(8) Å), and the N and O atoms of the bidentate-chelating ligand (Pt-N, 2.039(8); Pt-O, 2.026(7) Å); two Cl atoms are arranged in the apical positions (Pt-Cl, 2.301(3) and 2.312(3) Å). The five-membered chelate ring has a flattened gauche conformation with an NCCO torsion angle of 19(1)°.     

Stereoelectronic structure of 3-(trichlorogermyl)propionic acid by the results of <Emphasis Type="Italic">ab initio</Emphasis> calculations

Two structures of the 3-(trichlorogermyl)propionic acid molecule and its dimer were calculated by the RHF/6-31G(d) method with the full geometry optimization. The structure with pentacoordinated germanium atom is by 4.71 kcal mol^?1 more favorable than that with tetracoordinated germanium. The strength of coordination bond in the first structure increases with the absolute values of charge on the Ge and O coordination centers. The relatively small values of these charges result in a weak coordination bond. In the first structure, this bond is weaker than in the dimer, since the Ge…O distance in it (3.016 Å) is larger than in the latter (2.898 Å). This bond is formed due to the rapproachment of the Ge and O coordination centers at their electrostatic interaction. This provides the transfer of electron density from the atoms of the donor fragment of the molecule to the atoms of the germanium coordination polyhedron. The coordination centers serve as the conductors for the electron density transfer.     

Molecular and Crystal Structures of TeCl4-Allylalcohol and -Allylacetate Adducts

1,2-electrophilic addition of TeCl₄ to the C=C bond of allylalcohol is observed, while with allylacetate, 1,3-addition occurs, due to migration of the acetate group. The allylalcohol adduct comprises two different kinds of molecules in the solid state, Cl₃Te[CH₂CH(Cl)CH₂OH→] and Cl₂Te[CH₂CH(Cl)CH₂CH-], with dative Te←O and covalent Te-O bonds, five-membered ring structures and Cl-Te?Cl and O-H?O bridges linking the different molecules. In the allylacetate adduct, Cl₃Te[CH₂CH(CH₂Cl)OC(CH₃)=O→], a six-membered ring is formed via an intramolecular dative Te←O interaction, the molecules being linked via C-Cl?Te bridges. Multinuclear NMR spectroscopy and ¹H-¹H-NOESY combined with ab initio (MP2/LANL2DZP) geometry optimisation show the geometry of the ring structures in solution to be similar to those in the solid state.     

catena‐Poly­[[bis­(nitrato)(pyrimidine)­copper(II)]‐μ‐pyrimidine‐N:N′]

The title compound, [Cu(NO₃)₂(C₄H₄N₂)₂]_n, crystallizes as a linear polymeric compound with one pyrimidine ligand bridging between two Cu^II atoms and a second pyrimidine ligand coordinated in a monodentate manner. The distorted octahedral geometry around the Cu^II atom consists of two pyrimidine N atoms at distances of 2.033 (4) and 2.025 (4) Å, and two nitrate O atoms at distances at 1.987 (3) and 1.973 (3) Å. The apical positions are occupied by an N atom of a bridging pyrimidine ligand [2.291 (4) Å] and a nitrate O atom at a long distance of 2.781 (3) Å. The basal plane is almost planar, with trans angles of 176.23 (14) and 165.34 (15)°.